This invention relates to the art of mounting thin-walled metal honeycomb structures, such as those that would have utility as a substrate or heater in controlling emissions from a gasoline or diesel internal combustion engine. Such metal structures may be formed by extrusion from extrudable particulate metal batch materials which have the property of being able to flow or plastically deform during extrusion, while being able to become sufficiently rigid immediately thereafter so as to maintain their structural integrity, in the manner set forth in U.S. Pat. Nos. 3,790,654 and 4,758,272. Alternatively, the honeycomb structures may be fabricated from thin metal sheets such as by wrapping corrugated and uncorrugated metal sheets into a honeycomb structure as shown in U.S. Pat. Nos. 3,112,184 and 3,444,925. Further, if desired, the honeycomb structures could be made of pleated thin porous sheets of filter material whose layers are interleaved with corrugated or crimped spacers as disclosed in U.S. Pat. Nos. 2,884,091, 2,952,333 and 3,242,649.
The invention particularly relates to the problem of preventing degradation of the metal honeycomb substrate when utilized in and subjected to the harsh and rigorous conditions experienced in vehicular emissions control systems. When mounted in an exhaust stream of a vehicle, cellular metal honeycombs can be resistively heated for the purpose of accelerating the time in which pollutants may be converted. However, such mounted resistive heaters must withstand severe shock and vibration at elevated temperatures, which temperatures may exceed 920.degree. C. and such forces may exceed 20 g's. Even the relatively high temperature metals utilized in such cellular substrates exhibit a rather large and unfavorable reduction in mechanical properties as the temperature rises, potentially leading to heater distortion. Such distortion could result in electrical short circuits to ground, in the closure of resistance adjusting slots which would shorten the electrical path length, and in distortion of the flow cells which would compromise the gas flow therethrough.
It thus has been an object of the invention to provide a mounting system for metal honeycomb structures which not only protectively supports the structure within an enclosing housing, but also electrically insulates the metal honeycomb structure from such housing.